It may be just a build-up of dust inside the clutch. You'll soon see when you take the cover off.

It's pretty self-evident if the plates are worn: the first couple of friction plates wear the most; you may find the friction material worn completely away in places. There's not that much thickness to start with, mind.

You can "hide" worn plates nearer the back of the pack by swapping them around. Make sure you keep the dished plain plate in the same relative position, though. It's near the back.

Check the friction plate tangs and the grooves in the outer drum for wear. But don't be too picky about this, as long as the clutch isn't dragging, or you'll be changing clutches every five minutes.

Thanks for the info guys and I assume the overtightening screws is talking from experience!!

I haven't had time to get near it tonight but I intend to strip it down to stop the jerking it give me every now and again as it can cause the engine to stall.

Sometimes when I pull away you can feel it slip but only for a split second, the revs don't go up (that I notice), it just give a short squeek and lunges a bit, which is usually when I give it a bit too many revs when pulling away. This can sometimes lead to it stallling as it snatches.

I'm assuming that its correct to be putting the blame down to the clutch.